The invention relates to an optical device for reading and decoding bars of different reflectivity arranged in accordance with a barcode and adjoining one another, comprising an optical scanning device for scanning the bars by means of a light beam, a sensor for receiving the reflected light beam and the conversion thereof into an electrical sensor output signal, a transition detector for detecting the level tansitions in the sensor output signal and a decoding device which decodes the scanned barcode on the basis of the output signals from the transition detector.
A device of this type, in which the path from sensor to transition detector has been designed in analogue electronics, is generally known.
In practice the optical readers for reading and decoding barcodes are frequently confronted by a problematically low signal-to-noise ratio, in particular in the case of poorly printed barcodes and in the case of reading close to the edge of the read area. It is then not easy accurately to determine the transitions. These transitions are frequently determined by determining the peaks of the first derivative of the sensor output signal.